The invention relates to a method for operating a steering system for a motor vehicle and to a steering system.
The document DE 197 13 576 A1 discloses a steering system for a motor vehicle in which the steering movement of the driver is transmitted to a steering gear via the steering wheel and a steering shaft and the steering movement is converted by means of said steering gear into an actuating movement of the steered front wheels taking into account a transmission ratio. In order to support and boost the steering force which is generated by the driver, a servomotor is provided in which a motor actuating torque is generated as a function of the manual steering torque generated by the driver, and said motor actuating torque is transmitted to the steered vehicle wheels.
With such steering systems there is basically the problem that, in particular in order to trigger a steering movement, it is necessary for the driver to overcome an increased steering resistance which is due to system friction in the steering system. The system friction arises as a result of the interaction between moved mechanical parts in the steering system. The friction can basically be compensated by applying the motor actuating torque but, when a steering movement is initiated, there is the problem that the friction compensation does not become fully effective until the motor speed of the servomotor increases. Therefore, in the case of small steering movements the driver must apply an increased steering torque, which leads to a subjectively unpleasant steering sensation.